Power plant for helicopters



A. Y 5. FomssYTl-l 2,433,107

'- POWER PLANT FOR HELICOPTERS Filed Jan. 6, 1945 2 sheets-Sheet 1 .llIlllll 11.11.11111" 1 Dec. 23, 1947-.

A, G. FoRsYTH POWER PLANT FOR HEL'ICOPTERS Filed Jan. 6, 1945 2 sheets-$11961 2 WOR/VE Y Patented Dee. z3, 1941 i1 rowsa PLsN'rlFoa Haucor'raas Archibald Graham Forsyth. Chem. England, assignor to The Fairey Aviation Company Lim- -ited, Hayes. Middlesex, England Application January 0, 1945, Serial No. 571,800 In Great Britain August 31, 1944 o claims. (o1. 11o-135.5)

This invention relates to helicopters, the rotors of which are driven by internal combustion engines mounted at the outer ends of the rotor blades and has for its object improved means for carrying the high centrifugal loads which arise as a result of such a mounting.

To this end and in accordance with the present invention the internal combustion engines are mounted at the outer ends of arms, the inner ends of which are anchored to a rotor head at the top of a vertical, or normally vertical, rotor shaft, while the rotor blades are mounted on tubular shafts surrounding said arms, the inner ends of said tubular shafts being vmounted in sockets on the rotor head in bearings which en- "able said blades to move about longitudinal axes to vary their pitch angle and, at the same time, take up the loading due to the effect of centrifugal force on the blades themselves. As a result of this arrangement'the loading due to the effect of centrifugal force on the internal combustion engine units is taken up independently through the arms and their anchorage to the rotor head and no part thereof affects the bearings which resist the centrifugal force on the blades. In consequence pitch variation of the rotor blades may be effected without having to overcome undue resistance and the internal combustion engine units are not tilted in the fore and aft direction when such pitch variation takes place, as would be the case if said units were mounted directly on the outer ends of the blades.

The tubular shafts for the rotor blades may also have bearings between their outer ends and the arms which carry the internal combustion engine units.

Three forms of the invention are illustrated by Figures l, 2 and 3 of the accompanying drawings, respectively, each of which is a sectional elevation taken on a vertical plane in which lie the vertical axis of rotation of the rotor as a whole and the horizontal longitudinal axes of a pair of opposed rotor blades.

Referring first to Figure l it will be seen that a normally vertical rotor shaft a mounted to rotate in bearings (not shown) has at the sides of its upper end radially directed, vertically extending keys bb the outer surfaces of which lie on the surface of a sphere the centre c of which is on the axis of the rotor shaft a; for convenience this may be termed the main centre of the rotor. formed slots in heads dd at the inner ends of radially disposed arms ee at the outer ends of which internal combustion engine units ,ff are mounted. The inner and outer surfaces of these heads dd, i. e. those surfaces adjacent to, and remote from'the main centre c, respectively, are formed spherically, the inner surfaces being movable, arcuately on the keys bb of the rotor shaft c, and the outer surfaces abutting, when the unit carrying arms ce are subjected to centrifugal force, against the spherical inner surface of a hollow rotor head g. The rotor head g is formed with sockets hh, one for each rotor blade 71 and it is apertured correspondingly to give passage to the inner ends 'of the unit carrying arms ee. Within each socket h is arranged 'a thrust bearing k for the inner end of a tubular shaft m of a rotor blade i, the bearing lc being designed to permit rotation of said tubular shaft m and to take up the load due to the effect of centrifugal force on the blade d. The tubular shaft m surrounds, coaxiallya unit carrying arm e and a bearing n is disposed between its outer end and the unit carrying arm e. Owing to this arrangement of the parts the effect of centrifugal force on the units ff and on the blades id is transmitted independently to the rotor head g; moreover, the pitch angle of the rotor blades 9'1 can u be varied by turning them about the unit carrying arms ee without affecting the latter, consequently the units ff remain on an even keel, i. e. their fore and aft centre lines remain horizontal..

The rotor blades ii are arranged symmetrically opposite one another so that the rotor as a whole is balanced about the main centre c; it can however tilt about said centre relatively to the rotor shaft a which projects into the hollow rotor head g through an aperture in the bottom thereof. As shown in Figure 2, the rotor shaft a may be fixed, its upper end being surrounded by a spherical ball race o on which are provided keys pp for the heads dd of the unit carrying arms ee. In the form of the invention shown in Figure 3, the rotor shaft a is non-rotary, its upper end is surrounded by ball bearings qq supporting a sleeve r formed with keyways to receive the keys ss on the heads dd of the unit carrying arms ee, and the hollow rotor head g is mounted on the sleeve 1'. As, in this form of the invention, the rotor is not tiltable in relation to the upper end of the nonrotary shaft a said shaft may be universally mounted in a known manner, not illustrated, so

that its axis may be inclined to the vertical.

These keys bb fit into correspondingly The control means and otherdetails of the internal combustion engine lunits jf and the means for varying the pitch of the rotor blades if are not described and illustrated in connection with any of the above forms of rotor as any conventional mans may be used and they do not form part oi the present invention.

The use of internal combustion engines mounted at the ends of helicopter blades to rotate the blades by means of jet or propeller means is shown in prior art patents and'it is believed unnecessary to discuss these means in detail in this specification. These prior' art patents show the supplying of fuel to the engine units by tubing leading to the aircraft proper and also internal combustion engines which carry their own fuel supplies.

Various means for achieving pitch changes of helicopter rotor blades are shown in prior art patents to which reference may be had for further details.

I claim:

1. In a helicopter power plant of the type in which a rotatable blade assembly is rotated by means oi internal combustion enginesl provided at the outer ends of said blades, that improvement which comprises providing means for restraining said engines against movement away from the axis of rotation under the influence of centrifugal force, and means independent of said i'lrst named f means for restraining said blades against movement under the influence of centrifugal force.

2. In a helicopter power plant of the type in which a rotatable blade assembly carried by a rotor head is rotated by means of internal combustion engines provided at the outer ends of said blades, that improvement which comprises providing means for ,transmitting to said rotor head centrifugal forces acting on said engines, and means independent of said first named means for transmitting to said rotor head centrifugal force acting on said blades.

3. A power plant for helicopters, comprising a rotor shaft. a, rotor head carried by said shaft and having a plurality of sockets, thrust bearings in said sockets, a plurality of rotor arms each anchored to one end to said rotor head and carrying at its other end an internal combustion engine unit operable toL rotate said arms about a substantially vertical axis, a tubular shaft surrounding each of said rotor arms and cooperating with said thrust bearings so as to be restrained against axial movement but capable'of rotational pitch changing movement, and a plurality of rotor blades mounted oneon each of said tubular shafts. whereby the centrifugal forces acting on said blades and the centrifugal forces acting on said engine units are transmitted to said rotor head by independent means.

4. A power plant as set forth in claim 3 in which bearings are provided between the outerl ends of said tubular shafts and said rotor arms.

5. A power plant as set forth in claim 3 in which said rotor head is hollow and is provided with an internal bearing surface, and in which each of said rotor arms is provided at its inner end with a head abutting against said internal bearing surface.

6. A power plant as set forth in vclaim 3 in which said rotor head is hollow and is provided with an internal bearing surface, in which thel upper end of said rotor shaft extends within said rotor head and is provided with radially directed vertically extending keys on its peripheral surface, the outer surfaces of said keys lying on the surface of a sphere having its center on the axis ot the rotor v shaft, and in which each of said rotor arms is provided at its inner end with a head abutting against said internal bearing surface and having a slot which receives one of said keys.

7. A power plant as set forth in claim 3 in which said rotor shaft is rotary.

8. A power plant as set forth in claim 3 in which said rotor shaft is fixed, in which said rotor head is hollow and is provided with an internal bearing surface, in which a ball race carrying vertical keys is mounted about said rotor shaft, and in which each of said rotor arms is provided at its inner end with a head abutting against said internal bearing surface and provided with a slot cooperating with one of said keys.

9. A power plant as set forth in claim 3 in which said rotor shaft is non-rotary, in which ball bearings are provided about the upper end of said rotor shaft, a sleeve supported by said ball bearings and having vertical keyways therein, and a head ron the inner end of each of said rotor arms and provided with keys cooperating with said keyways, the rotor head being hollow and mounted on said sleeve.

ARCHIBALD GRAHAM FORSYTH.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS 

